Current orthopedic practice employs basically the same processes and materials for immobilizing an extremity which have been used for years. Regarding splinting and casting appliances, there are several different types of approaches currently being practiced. These can generally be characterized as various plaster composites as well as malleable aluminum plates and rods and other devices such as sticks, boards and inflatable balloons and cardboard materials.
Plaster-based composites are calcium sulfate impregnated textile fabrics such as cotton cheesecloth or gauze. These plaster-based splinting and casting orthoses must be configured in the presence of the patient and are built up by combining either sheets or rolls of plaster-based composite materials in gauze or stockinettes followed by elastic wraps. These materials are quite fragile within the first few hours of construction and are subject to easy breakage. Even upon drying, they are very heavy and suffer from a number of disadvantages, such as a lack of breathability, and are incapable of producing an orthopedic device which is anything but radio-lucent. Further, plaster of paris is, by its very nature, hydrophilic which means that moisture is retained within the cast which in turn provides an ideal breeding ground for bacteria and fungi on sites next to the skin.
Due to the inherent disadvantages present in the use of plaster of paris materials, recent interest has been focused towards suitable replacements. As illustrative, water dip fiberglass/urethane resins splints and casts are entering the market but are not in general use. Some medical professionals have expressed concern about a lack of moldability of such materials as the inelasticity of fiberglass/urethane materials is well-known. These characteristics are translated into a spiral wrapping which tends to be extremely brittle, resulting in a flare up of "pressure sores" commonly experienced by the user of such orthoses unless the medical practitioner is extremely versed in their application. This inherent stiffness also means that fiberglass-based casting tapes are virtually impossible to mold onto the injured appendage.
U.S. Pat. Nos. 3,089,486 and 3,908,644 teach the use of acrylic monomers, i.e., having the general structure H.sub.2 C.dbd.CR.sub.1 R.sub.2 wherein R.sub.1 is usually a hydrogen atom or a methyl group and R.sub.2 is usually a carboxylic acid group or its ester. These monomers are polymerized to produce hardenable members; however, systems employing these materials are fraught with disadvantages. Being free radical polymerizable, an external source of free radicals is needed as well as a reaction initiator such as ultraviolet light. Further, the monomers are skin penetrants and thus barriers are absolutely necessary to protect the user from these potentially toxic materials. Their shortcomings are further manifested by the fact that most if not all acrylic monomers exhibit a strong and objectionable odor which makes them unsuitable as major components for orthoses. Lastly, such monomers characteristically do not polymerize "rock" hard, take too long to polymerize to make such casting systems convenient to use, and traditionally employ flammable solvents resulting in a rather hazardous system.
U.S. Pat. Nos. 4,376,438 and 4,411,262 disclose resin systems which can be characterized as "condensation comonomers," i.e., diisocyanates and polyols. Such monomers are usually employed by preparing a premix of these materials with a catalyst in the absence of moisture and air. The catalysts generally employed are such things as mercuric or tin amine or imine, all of which are potentially toxic. In use, diisocyanate-based systems require a water dip to unblock the stabilized monomer.
It is one of the objects of the present invention to provide a self-contained kit which eliminates the need for the use of any external ingredient, such as water, not contained in the kit.
It is a further object of the present invention to develop a casting system which could be provided in a completely self-contained kit which is lighter and easier to use than prior plaster and fiberglass casts, would require only modest expertise to use, and yet exhibit excellent moldability, be completely X-ray transparent, substantially water resistant, and develop less of an exotherm during hardening or setting.
It is still a further object of the present invention to provide a cast or splint which exhibits a relatively high modulus of elasticity enabling the orthosis to absorb stress by slight bending rather than cracking, a result which is most uncharacteristic of plaster and fiberglass orthopedic members.
It is yet another object of the present invention to provide a cast or splint system which is available in a completely self-contained kit form while producing splints and casts having those advantages over the prior art as recited previously.
It is still another object of the present invention to provide cast and splint members as well as methods for their fabrication and use wherein the cast and splint members are significantly more water-repellant and resistant than plaster or fiberglass cast materials and are of a lighter weight and thus when wet, dry considerably quicker than their prior art counterparts. Significantly, the casts and splints manufactured pursuant to the present invention are considerably more porous than prior orthoses which should aid in breathability and thus promote a healthier skin condition during long-term usage.
It is finally an object of the present invention to provide cast and splint systems in which the hardening agent would autocatalytically cure at ambient conditions without resorting to externally applied heat, pressure, enhancers, oxidizers, ultraviolet light, peroxides or other initiators or promoters.